The manufacture of axial profiling of a thin-walled, cylindrical hollow part (hereinafter, “workpiece”) can, for example, be carried out by means of a cold rolling process. Accordingly, methods are known, wherein rotational tools, designated as profiling rollers, which are confined in circular orbits, are caused to repeatedly impact against the circumferential surface of a workpiece. By means of an axial progression of the workpiece relative to the profiling tool and with the aid of axially toothed mandrels, the desired toothing can be realized. Profiling in this manner is effective in producing internal and external toothing in the thin wall of the said cylinder. However, a continual disadvantage of this conventional method, attributable to varying diameters of the profiling tool orbits, is that the produced longitudinal toothing profiles possess curvatures with radii which are larger or smaller than desired.
Another disadvantage of the above described method of cold forming by means of profiling rollers, lies in the fact that toothing on a workpiece which possesses an annular shoulder, cannot be brought up tightly against the said shoulder. Limited by the diameter of the said orbit of the profiling roller, a defined section of the workpiece remains unchanged between the termination of the axial extent of the profiling and the shoulder, which cannot be subjected to profiling action.
Thus, the purpose of the present invention is to find a method and an apparatus, which will permit an exact toothing of thin-walled, cylindrical hollow bodies corresponding to a specified geometry, wherein the clearance to a shoulder is minimized.
This purpose is achieved, in accord with the invention, with a method for profiling of a cylindrical, thin-walled, hollow workpiece by cold-forming, comprising: creating a profile running essentially parallel to a longitudinal axis of the hollow workpiece by means of at least one profiling tool arranged externally to said hollow workpiece and carrying out, in a direction radial to said longitudinal axis, hammering metal working impacts against the workpiece; the at least one profiling tool executing its metal-working impacts onto an external surface of the workpiece while oscillating in a direction essentially perpendicular to said longitudinal axis; and accomplishing a relative movement of said profiling tool and said workpiece in axial direction while maintaining constant a radial profiling depth setting, until a desired axial length of profiling on the workpiece is achieved; wherein the profiling tool is designed as a metal working die comprising an active operational side having in a plane perpendicular to said longitudinal axis a cross-section corresponding to the contour of the profile to be created in the external surface of the workpiece, the active operational side having a lower edge which is inclined at an acute angle relative to said longitudinal axis, except for a calibration zone which is aligned parallel to the longitudinal axis, wherein said calibration zone forms an end portion of said lower edge, and wherein said calibration zone is that portion of said lower edge which is located closest to the surface of the workpiece.
And, this purpose is also achieved by means of a method for profiling of a cylindrical, thin-walled, hollow workpiece by cold-forming, comprising: creating a profile running essentially parallel to a longitudinal axis of the hollow workpiece by means of at least one profiling tool arranged externally to said hollow workpiece and carrying out, in a direction radial to said longitudinal axis, hammering metal working impacts against the workpiece; the at least one profiling tool executing its metal-working impacts onto an external surface of the workpiece while oscillating in a direction essentially perpendicular to said longitudinal axis; accomplishing a relative movement of said profiling tool and said workpiece in axial direction while maintaining constant a radial profiling depth setting, until a desired axial length of profiling on the workpiece is achieved; and intermittently rotating said hollow workpiece about said longitudinal axis, wherein said intermittent rotation of the workpiece is synchronized with the oscillating movement of the profiling tool.
In addition, this purpose is achieved by means of an apparatus disclosed herein.
Attention is called to the invented method for the cold rolling profiling of the workpieces, wherein, essentially, splines or teeth are circumferentially apportioned about the said workpiece. These teeth extend, for example, parallel to the longitudinal axis of the workpiece, whereby at least one externally placed profiling tool is applied. This profiling tool produces repeated impacts against the circumferential wall of the workpiece in a direction transverse to the said longitudinal axis thereof. In this way, a hammering operation is furnished, whereby the said profiling tool continually oscillates essentially in a resulting radial direction against the surface of the workpiece, thus achieving the desired metal shaping. In addition, the profiling tool, besides operating in a uniform radial depth oscillation, is also caused to move axially along the length of the workpiece, up to a predetermined, axial length of the desired toothing.
In this way, in a single manufacturing operation, the toothed profile has been made throughout its entire specified length. Simultaneously, the tooth shaping and cold-rolling operations have been consolidated into a multiplicity of incremental steps. Accordingly, it becomes advantageously possible to hold the functional effect of each incremental step at a relatively small level. This leads to obtaining a high degree of precision of the produced profiling, that is to say, of both the inner and the outer formation of teeth, and accordingly allows a superior formation of the said toothing. Especially, it is possible, with the invented method, to produce profiled teeth, for example, of relatively small radii. This ability permits that part of the workpiece wall, which carries the said precise profiling, to be extended to a decisively increased distance with identical toothing. On this account, the profiling tool, giving consideration to its radially oriented motion relative to the circumference of the workpiece, can be axially run to a profiling position proximal, within a close tolerance, to the said annular shoulder about the workpiece, so that thereby, profiling up to a narrow clearance from said shoulder becomes possible. The advantage lies therein, in that the profiling tool performs practically no uncontrolled motion of its own in the axial direction and thereby no free wobble-room in the axial direction of the working surface becomes a disadvantage.
In an exemplary manner, preliminary to its axial movement, the profiling tool can be adjusted to a predetermined profile depth, measured radially to the longitudinal axis of the workpiece. Because of the fact, that the profiling tool, preliminarily to the actual metal working process, has been radially placed in a position external to the workpiece, sufficient free installation space in the workpiece exists so that the said profiling tool can be easily connected to a holding mechanism.
Advantageously, it is possible, that at least once, a change of direction of the axial transport direction relative to the profiling tool and the workpiece can be carried out. This is advantageously done following the reaching of the specified length of the toothing. Specifically, the said changed direction is a retraction to the original start-position of the profiling tool relative to the workpiece. In this way, very high demands for precision and surface conditions of the toothing itself can be fulfilled.
Consideration can also be given to multiple back and forth traverses of the workpiece in the axial direction, these movements being relative to the profiling tool. This reciprocal movement would be intended to obtain a desired degree of surface quality.
In an exemplary manner, respectively following the conclusion of its relative axial movement, the profiling tool is radially lifted out of the toothing of the workpiece. When this conclusive event has been completed, then the finally completed workpiece can be simply removed from the metal working machinery and a new, so-called raw workpiece inserted therein. With the invented method, it is possible, that, advantageously, a predetermined profiling, such as, for instance, a toothing with a specified inter-spacing could be produced.
For instance, an oscillatory thrust motion of the profiling tool can be adjusted to be greater than the maximum radial depth of impression of the profiling tool into the workpiece. In such a situation, the workpiece can be, advantageously, intermittently rotated about its axis, namely in synchrony with the oscillating thrust action. This synchronized adjustment also, advantageously, determines the spatial separation distance of the profiling to be made.
Advantageously, it is possible to operate the profiling tool at more than 1000 impacts per minute, preferably at even more than 1500 impacts per minute. In this way, very high rates of production can be achieved, which is of advantage for the mass production of the auto industry.
In addition, the workpiece under production is superimposed upon a complementarily toothed mandrel, whereby the said mandrel is in impacting opposition to the profiling tool. With this aid, both the outer—as well as the inner—profile of the workpiece can be quickly and precisely fabricated.
For example, the profiled zone of the mandrel can extend from its free end to a radially, projecting annular shoulder and the open end of a workpiece is set thereupon, wherein the said workpiece also exhibits a surrounding shoulder, i.e. in other words, possesses a limiting obstruction to further profiling tool advance. Such workpieces find application in automotive motor construction, for instance serving for the transfer of rotary motion and torque in automatic transmissions. In this application, the extent of the profile must extend itself in design and manufacture as an exact inner and outer toothing, closely approaching in an axial direction the outward projecting collar of the workpiece.
For example, if the profiling tool, during the first part of the operative method, be brought into proximity of the shoulder of the mandrel, that is to say, into that section of the end section of the workpiece which is radially subjected to profiling, then subsequently, during the second part of the operative method, the said mandrel is axially and slidingly displaced away from the said profiling tool. As these stated occurrences take place, then either the profiling tool or (advantageously) the workpiece can be axially moved by the metal working machine, in order to effect a controlled, axial, relative displacement between the said workpiece and the profiling tool. This relative movement is carried out for such a length of time until the axial distance is reached, wherein the profiling tool can no longer operate in profiling the workpiece. Further, this said movement is designated as being carried out under tension, i.e. by a “pulling action”, since the profiling tool, practically immediately after a workpiece-impression operation, is pulled along, until the entire specified length of the profiling has been completed.
For example, the profiling tool is initially designed to operate at the free end of the workpiece, that is, to be adjusted to a radially opposing configuration against the said mandrel, wherein the said mandrel or the workpiece can be moved axially along the workpiece, until blocked by the said shoulder. This movement would continue until the profiling tool has reached a point immediately proximal to the shoulder of the mandrel, in other words, the said movement continues over a specified distance wherein the circumference of the workpiece is to be subjected to metal working. Even in this case, obviously, it is possible that the relative interactive work between the profiling tool and the workpiece can be carried out by means of an axial sliding of the workpiece.
This axial displacement is looked upon as an impact centered movement, since the profiling tool primarily shapes and completes the profiling of the circumference of the workpiece. In this way, it is possible that the said tool, while yet separate from the free end of the workpiece, can be adjusted to a predetermined toothing depth and only thereafter be functionally applied to the workpiece.
As an example, the profiling can be carried out, respectively, by at least two profiling tools, which are situated radially opposite to one another. The profiling tools of this pair of profiling tools, are advantageously driven in concert with one another in conformation with their radial disposition and their synchronized oscillatory motion. Thereby, an optimal apportionment and application of profiling force can be assured. Again, in an exemplary manner, the profiling tool can be adjusted for radial motion in relation to the workpiece, in a continual or discrete stepwise manner, to attain the desired final profile depth on the workpiece.
In accord with the invention, the stated purpose thereof can be achieved by means of an apparatus having the features as disclosed herein. Additional, advantageous, invented embodiments of the apparatus become evident by reference to the features of the apparatus disclosed herein.
The apparatus comprises at least one eccentrically operated drive; at least one profiling tool operationally connected to said at least one eccentrically operated drive; a workpiece holder in the form of a mandrel for holding a hollow workpiece, said workpiece holder being movable along a longitudinal axis of the mandrel relative to said profiling tool; a drive for rotating said mandrel about said longitudinal axis; wherein the profiling tool is designed as a metal working die comprising an active operational side having in a plane perpendicular to said longitudinal axis a cross-section corresponding to the contour of the profile to be created in an external surface of a hollow workpiece held by said workpiece holder, the active operational side having a lower edge which is inclined at an acute angle relative to said longitudinal axis, except for a calibration zone which is aligned parallel to the longitudinal axis, wherein said calibration zone forms an end portion of said lower edge, and wherein said calibration zone is that portion of said lower edge which is located closest to said mandrel.
In accord with the invention, the apparatus possesses, for the purpose of carrying out the invented method, at least one, operationally active, profiling tool holder having an eccentrically operated drive. The said apparatus further encompasses: a mandrel capable of (relatively) of being axially and slidably displaced in reference to the said axially aligned profiling tool holder and/or the holder for the workpiece; a drive for the axis-centered rotation of the mandrel and for the workpiece holder; and at least one profiling tool, designated also as a metal shaping die. In this arrangement, the said die possesses a working profile, which, as a die, corresponds to the shape of the external contour of the incipient workpiece profile. Additionally, the said working profile of the tool, in other words, the operational impacting surface, can be adjusted to an acute angle relative to the longitudinal axis, however, with the exception of a zone thereof, which is radial to the smallest possible distance away from the circumferential surface of the workpiece and which is designated as a calibration area running parallel to the longitudinal axis of the said workpiece. Thereby, the said calibration area is the first to make an impression on the surface of the workpiece, since this contacted zone of the said surface has the greatest proximity to the said profiling tool. After an impression by the calibration zone, it is especially possible, due to cold working properties of the thin metal of the workpiece, that respectively also the remainder of the die surface (other than the calibration zone) impinges into the said circumferential surface, and a preliminary, initial metal working of the workpiece thereby takes place. In the second part of the method, the die, which has a constant radial adjustment, moves axially along the circumference of the workpiece, then the said calibration zone is required to take upon itself a subsequent start of the formation of the desired profile.
Again, as an example, the depth of the die impression, i.e., the depth of the profile of the working tool, is made deeper than the depth of the profiling to be accomplished on the workpiece. Accordingly, for example, during the progressive, stepwise axial displacement of the workpiece, the entire, radially adjusted, predetermined depth of the profile is obtained
For instance, the length of the calibration zone corresponds to only a fraction of the entire axial length of the profiling, that is to say, the entire length of the operational profile. This calibration zone is, finally, a governing element for the formation and the precision of the profiling, since, at the end of the radial adjustment only this calibration zone comes into contact with the workpiece. Advantageously, the profiling die of the profiling tool is made of high-strength material and possesses, for example and has been subjected to an appropriate heat treatment, so that the longest possible operational life can be obtained and therewith a high degree of precision of the produced profiling, even at the cost of a longer period for mandrel construction.
The apparatus possesses at least two, profiling tools, each of which lies opposite to the other in a line transverse to the longitudinal axis of the hollow, cylindrical workpiece. Accordingly, an optimal input of force and apportionment thereof is assured for the workpiece. Even the forces in the apparatus itself can be optionally picked up and properly distributed. Consideration may be given to other arrangements, advantageously respective symmetrical alignments of the profiling tools.